1 files changed, 25 insertions, 10 deletions
diff --git a/src/gl3_impl.zig b/src/gl3_impl.zig
index b056056..1e6ce23 100644
--- a/src/gl3_impl.zig
+++ b/src/gl3_impl.zig
@@ -29,24 +29,18 @@ pub fn Init() void {
     io.*.BackendRendererName = c"imgui_impl_gl3.zig";
     if (OpenGLHasDrawWithBaseVertex)
         io.*.BackendFlags |= @enumToInt(c.ImGuiBackendFlags_RendererHasVtxOffset);
-    // @TODO: Viewports
-    // io.*.BackendFlags |= @enumToInt(c.ImGuiBackendFlags_RendererHasViewports);
+    io.*.BackendFlags |= @enumToInt(c.ImGuiBackendFlags_RendererHasViewports);
 
     // @TODO: GLSL versions?
     // g_GlslVersionString = g_GlslVersionString_buf[0..glsl_version.len];
     // mem.copy(u8, g_GlslVersionString, glsl_version);
 
-    // @FIXME: just for testing:
-    var tex: c.GLint = undefined;
-    c.glGetIntegerv(c.GL_TEXTURE_BINDING_2D, &tex);
-
-    // @TODO: Viewports
-    // if (io.*.ConfigFlags & @enumToInt(c.ImGuiConfigFlags_ViewportsEnable) != 0)
-    //   InitPlatformInterface();
+    if (io.*.ConfigFlags & @enumToInt(c.ImGuiConfigFlags_ViewportsEnable) != 0)
+       InitPlatformInterface();
 }
 
 pub fn Shutdown() void {
-    // ImGui_ImplOpenGL3_ShutdownPlatformInterface();
+    ShutdownPlatformInterface();
     DestroyDeviceObjects();
 }
 
@@ -447,3 +441,24 @@ fn SetupRenderState(draw_data: *c.ImDrawData, fb_width: i32, fb_height: i32, ver
     c.glVertexAttribPointer(@intCast(c.GLuint, g_AttribLocationVtxUV), 2, c.GL_FLOAT, c.GL_FALSE, @sizeOf(c.ImDrawVert), @intToPtr(?*c.GLvoid, @byteOffsetOf(c.ImDrawVert, "uv")));
     c.glVertexAttribPointer(@intCast(c.GLuint, g_AttribLocationVtxColor), 4, c.GL_UNSIGNED_BYTE, c.GL_TRUE, @sizeOf(c.ImDrawVert), @intToPtr(?*c.GLvoid, @byteOffsetOf(c.ImDrawVert, "col")));
 }
+
+// Platform Interface (Viewport Feature)
+// -------------------------------------
+
+fn InitPlatformInterface() void {
+    const platform_io = c.igGetPlatformIO();
+    platform_io.*.Renderer_RenderWindow = Platform_RenderWindow;
+}
+
+fn ShutdownPlatformInterface() void {
+    c.igDestroyPlatformWindows();
+}
+
+extern fn Platform_RenderWindow(viewport_: ?*c.ImGuiViewport, cookie: ?*c_void) void {
+    const viewport = viewport_ orelse unreachable;
+    if (viewport.*.Flags & @enumToInt(c.ImGuiViewportFlags_NoRendererClear) != 0) {
+        c.glClearColor(0.0, 0.0, 0.0, 0.0);
+        c.glClear(c.GL_COLOR_BUFFER_BIT);
+    }
+    RenderDrawData(viewport.*.DrawData);
+}